In the field of optical data communications, data is generally transmitted using variations in light intensity. For instance, a high optical power (P1) or low optical power (P0) may be used to represent the logical bits one and zero, respectively. FIG. 1 shows the relation between an exemplary optical signal 100 and its corresponding logical signal 120 or bit pattern 130.
Optical transceivers send and receive data in an optical form over an optical link, such as a fiber-optic link. An optical transmitter can include laser driver circuitry to drive a laser diode (LD) and create optical pulses on the fiber-optic link from received electronic signals. An optical receiver can include a photosensitive diode to receive the optical signals, which are then converted into electronic signals. Thus, an optical transceiver converts (i) optical signals into analog and/or digital electronic signals, and (ii) electronic signals into optical signals.
In order to determine if the optical transceiver is functioning correctly, various operational parameters relating to the optical signal may be monitored. An extinction ratio, an average power and an optical modulation amplitude are examples of such parameters and can be useful indicators of the “health” of the transmitter of an optical transceiver.
The average power (Pavg) of the exemplary optical signal can be determined according to the equation:Pavg=(P1+P0)/2  [1]where P1 is the power of the signal corresponding to a “1” state, and P0 is the power of the signal corresponding to a “0” state.
An extinction ratio (ER) is a measure of depth of modulation, and is equal to the ratio between the high (P1) and low (P0) power levels of the optical signal. ER can be calculated according to the equation:ER=P1/P0  [2]where P1 is the power of the signal corresponding to a “1” state, and P0 is the power of the signal corresponding to a “0” state. An ER may be expressed as a ratio, percentage or decibel (dB). An optical oscilloscope is typically used to generate a representation of the optical signal from the optical transceiver, from which the ER is generally calculated. As such, conventional optical transceivers do not typically calculate the ER of optical signals they send and/or receive.
The optical modulation amplitude (OMA) is the difference between the high (P1) and low (P0) power levels of the optical signal. OMA may be calculated according to either of the following equations:OMA=P1−P0  [3]OMA=2Pavg[(ER−1)/(ER+1)]  [4]where P1 is the power of the signal corresponding to a “1” state, and P0 is the power of the signal corresponding to a “0” state. Conventional optical transceivers typically do not determine the optical modulation amplitude (OMA) of an optical signal. The link budget of an optical link is a direct function of the OMA of the signal.
This “Discussion of the Background” section is provided for background information only. The statements in this “Discussion of the Background” are not an admission that the subject matter disclosed in this “Discussion of the Background” section constitutes prior art to the present disclosure, and no part of this “Discussion of the Background” section may be used as an admission that any part of this application, including this “Discussion of the Background” section, constitutes prior art to the present disclosure.